I. Field of the Invention
The present invention relates generally to ventilating systems for buildings and, more particularly, to means for removing heat and fumes from above a working surface in a kitchen area and returning fresh air to the working area, which fresh air is preheated.
II. Description of the Prior Art and Patentability Statement
Exhaust hoods designed for permanent installation over stoves and, particularly, cooking appliances in commercial kitchens of the type which are particularly adapted for use for frying, broiling and grilling are well known in the prior art. Typically, such exhaust hoods are provided with a duct system and a fan of some type so that the hood captures most of the smoke, vapors and odors given off and exhausts these heated gases through an exhaust duct to the outside of the building in a continuous manner. Prior art exhaust hoods, and particularly those disclosed in U.S. Pat. Nos. 3,800,689, 3,890,887, and 3,837,269, have made provisions for providing fresh, cool air through the exhaust hood. Typically, this fresh air is injected by the exhaust hood downward at the front thereof which achieves a number of desirable objectives. Since the exhaust hood normally overlaps the cooking surface, this air is injected generally in the regions where the cooks are standing, thereby providing cooler working conditions and a deterrent to the flow of smoke upwardly from the capture area of the exhaust hood. It also provides a controlled filter replacement for the air, smoke and the like exhausted and makes the exhausting easier. One significant concern of those who pay fuel bills for buildings is the cost of heating fresh air introduced into the building to make up for air exhausted. The volume of air involved can be particularly large in restaurants having large hoods with high exhaust capacity for the removal of fumes and contaminants from the kitchen.
Of the above identified patents, U.S. Pat. Nos. 3,837,369 and 3,800,689 each disclose kitchen ventilating hoods that are disposed over the cooking appliance in a kitchen, and each has an exhaust duct and a return duct. The systems are both similar in that they are provided with means for bypassing some of the hot air exhausted from the kitchen to return the bypassed portion back to the kitchen so as to preheat some of the air being brought in from the outside. U.S. Pat. No. 3,890,887 illustrates a more conventional hood wherein cold air is returned to the kitchen, while hot air is exhausted therefrom. U.S. Pat. No. 3,521,582 discloses a heating system wherein hot air from a conventional furnace preheats the fresh air coming into the furnace as the hot exhaust gases are exhausted from the furnace. While there are similarities in the aforementioned prior art apparatuses to that disclosed in the instant application, it is the inventor's belief that the subject matter disclosed and claimed herein constitutes a patentable improvement over the prior art.